By Ellen Wulfhorst
NEW YORK (Reuters) - A fatal New York City train derailment last year was likely caused by the engineer at the controls who fell asleep due to an undiagnosed sleep disorder, the U.S. National Transportation Safety Board said on Tuesday.
The Manhattan-bound commuter train was traveling more than 50 miles per hour (80 km per hour) faster than the speed limit when it rounded a curve and derailed shortly after 7 a.m. on Sunday, Dec. 1, 2013, the NTSB said in its findings.
Four people were killed and at least 61 people were injured in the derailment of the Metro-North Railroad train, it said.
The engineer had severe obstructive sleep apnea that had not been diagnosed, the NTSB said. With such apnea, the airway collapses or becomes blocked during sleep, according to the National Institutes of Health website. The condition can cause drowsiness.
Neither Metro-North nor federal regulations require medical screening to detect sleep disorders, the NTSB said.
The engineer's sleep disorder was exacerbated by a change in his work schedule, it said. He had been moved to an early-morning shift about two weeks before the crash.
The engineer, William Rockefeller Jr., told investigators that a "hypnotic" state overcame him before he realized his train was derailing, according to previously released NTSB documents.
"I was dazed, you know, looking straight ahead, almost like mesmerized," Rockefeller told investigators.
A factor in the severity of the accident was the loss of glazing that seals the train's windows, which resulted in the fatal ejection of four passengers, the NTSB said.
Also contributing was the lack of a system on the train that would have automatically applied the brakes to enforce the speed limit, it said.
The train was traveling at 82 mph (132 kph) in a zone where the maximum authorized speed was 30 mph (48 kph), it said.
Bound for Grand Central Terminal, the early-morning train departed from Poughkeepsie, New York. All seven passenger cars and the locomotive derailed.
An estimated 115 passengers were on board at the time of the derailment, it said.
(Reporting by Ellen Wulfhorst; Editing by Eric Beech)